pytest.cursorrules

# pytest Cursor Rules

You are an expert in pytest testing. Follow these rules:

## Structure
- Name test files test_*.py or *_test.py. Name test functions test_*
- Group related tests in classes (class TestUserAuth:) — no __init__ needed
- Use descriptive names: test_login_fails_with_expired_token over test_login_3
- One assertion concept per test — multiple asserts are fine if testing one behavior

## Fixtures
- Define fixtures in conftest.py for shared setup — pytest discovers them automatically
- Use @pytest.fixture with appropriate scope: function (default), class, module, session
- Yield fixtures for setup/teardown: yield resource then cleanup after
- Use factory fixtures (fixture that returns a factory function) for parameterized setup
- Request fixtures by name in test parameters — no imports needed

## Parametrize
- Use @pytest.mark.parametrize("input,expected", [...]) for data-driven tests
- Use ids parameter for readable test names: ids=["empty", "single", "overflow"]
- Stack multiple parametrize decorators for combinatorial testing
- Use pytest.param(..., marks=pytest.mark.xfail) for expected failures in param sets

## Markers
- Use @pytest.mark.slow, @pytest.mark.integration — register in pytest.ini/pyproject.toml
- Run subsets with -m "not slow" or -m integration
- Use @pytest.mark.skipif(condition, reason="...") over bare skip
- Use @pytest.mark.usefixtures("db") when you need the fixture but not its value

## Assertions & Patterns
- Use plain assert — pytest rewrites them for detailed failure output
- Use pytest.raises(ExceptionType, match="pattern") as context manager
- Use pytest.approx() for float comparisons: assert result == pytest.approx(3.14, abs=1e-2)
- Use tmp_path fixture for temp files, monkeypatch for env vars and attributes

## Configuration
- Configure in pyproject.toml [tool.pytest.ini_options] — not pytest.ini or setup.cfg
- Set testpaths, markers, addopts (e.g., -ra --strict-markers)
- Use --strict-markers to catch typos in marker names
- Use conftest.py at project root for shared fixtures, in subdirs for scoped ones